1. Field of the Invention
The present invention relates to a biological process of producing p-hydroxybenzoic acid. Also, the present invention relates to a process of producing p-hydroxybenzoic acid through the chemical and/or biological conversion from lignin as a raw material.
2. Description of the Related Art
Steadily increasing oil prices and an increase in the price of basic fractions, such as naphtha, has given rise to a rapid increase in the price of petrochemical products. As an alternative to the petrochemical industry's dependence on crude oil, industrial biotechnology (also known as white biotechnology) has attracted intensive attention for its use of biomass to produce alternatives to conventional energy and production methods thereof; and additionally for its applications in other fields, including bioenergy, bioplastics, and biocompounds.
The market of bioplastics produced from biomass has rapidly expanded since Cargill-Dow successfully commercialized polylactic acid (PLA) in 2002, which is a substitute for pre-existing plastics, including polyethylene terephthalate (PET) and polystyrene (PS). In addition, polyhydroxyalkanoate (PHA)-based bioplastics, developed and commercialized by Metabolix earlier than PLA, are ready for entry into the market of general-purpose polymers from the market of expensive medical polymers as Metabolix constructed relevant plants. Polybutylene succinate (PBS) products, which involve succinic acid, are also widely commercialized and utilized.
Turning to biochemical products, a successful example of replacing a conventional petrochemical process with an industrial biotechnology process is 1,3-propandiol, commercialized by DuPont in-2006. In the future, industrial biotechnologies for various chemical products are expected to be developed and used in place of conventional petrochemical processes.
Aromatic hydroxycarboxylic acids, particularly p-hydroxybenzoic acid, salicylic acid and 2-hydroxy-3-naphthoic acid, have long been known for utility as raw materials in preservatives, medicines, dyes, pigments, etc. In addition, they have recently drawn extensive attention for utilization as monomers for aromatic polyesters as well as raw materials for agricultural chemicals, and color developing agents of thermal paper. The chemical p-hydroxybenzoic acid is used as a main monomer which accounts for 65% of the liquid crystal polymer Zenite™, manufactured by Ticona. This liquid crystal polymer is widely applied to automotive parts and electronics industries due to its higher than conventional general-purpose resin strength/stiffness, heat stability, organic solvent tolerance, lower melt viscosity, and gas permeability. Moreover, p-hydroxybenzoic acid can be converted via esterification into paraben, which is widely used as a preservative in cosmetics, hygienic goods, daily supplies, and foods.
For chemical synthesis of p-hydroxybenzoic acid, a method based on the Kolbe-Schmitt reaction from phenol and carbon dioxide (JP 05-009154), and modifications thereof (U.S. Pat. Nos. 5,399,178, 4,740,614, 3,985,797) were reported. However, the chemical synthesis methods of p-hydroxybenzoic acid cause various significant problems in production processes, in addition to requiring high production costs. In practice, chemical synthesis methods force workers to face environmental dangers of high temperatures and high pressures, require complex separation and purification procedures for by-products formed after the reaction, and produce environmental pollution due to chemical wastes formed during the separation and purification procedures.
The biological production of p-hydroxybenzoic acid was introduced by the microbial production of p-hydroxybenzoic acid from benzoic acid, p-cresol, toluene, etc. (JP 06-078780, Whited and Gibson, J. Bacteriol. 173:3010-3020 (1991), US20060246559, WO2005/103273). However, the starting materials are toxic to microbes, making the scale-up of the production difficult.
In 1998, DuPont developed a technique for producing p-hydroxybenzoic acid from glucose using Pseudomonas mendocina (WO1998/056920). The microbial production of p-hydroxybenzoic acid from glucose was successfully implemented in recombinant E. coli by GE in 2000 (U.S. Pat. No. 6,030,819). Ramos et al., of North Carolina State University, succeeded in developing p-hydroxybenzoic acid resistant bacteria containing a Psudomonas putida-derived tonB, a p-hydroxybenzoic acid-tolerant gene in 2008 (U.S. Pat. No. 7,348,421). In addition, Frost et al, of Michigan State University, produced p-hydroxybenzoic acid at a concentration of 12 g/L from glucose in E. coli in 2001 (Biotechnol Bioeng. (2001) 76(4):376-90).